One form of electrically heated coffee making machine comprises a flat through-flow or continuous flow heater assembly which is disposed beneath a plate for supporting and warming a coffee pot and thus keeping the coffee therein hot. The heater unit comprises a tubular heater member disposed directly underneath the support and warming plate, while a water pipe for carrying a flow of water therethrough is arranged in contact with the tubular heater underneath and outside same. Although that construction has the advantage that the support plate is adequately heated by the tubular heater so that the infusion beverage, namely the coffee, is kept hot in the coffee pot which is disposed on the support plate, nonetheless the transfer of heat from the tubular heater to the water pipe is in an inclined and upward direction, that is to say, into the steam space in the water pipe. That means that the efficiency of the arrangement is substantially impaired, in regard to pushing the column of water up into a riser pipe to produce a flow of water through the coffee grains, thereby to produce the coffee. In addition, as the heated steam issues from the riser pipe, it tends to produce an unpleasant snorting noise which is often unacceptable to modern consumers. In addition, there is the further consideration that the generation of unnecessary steam, which may often be about one fifth of the quantity of water to be heated by the heater, gives rise to unnecessary consumption and thus wastage of energy, which is also unacceptable under modern-day conditions. A coffee making machine of the kind just discussed is disclosed for example in German laid-open application (DE-OS) No. 26 42 571.
In a similar form of an electrical continuous flow heater, the tubular heater and the water flow pipe are arranged one beside the other. That arrangement also provides that the flow of heat from the tubular surface to the water pipe is by way of the side surface thereof, while the predominant part of the heat is also transferred into the steam space in the water pipe, with the attendant disadvantages as referred to above. Such a construction is to be found for example in German laid-open application (DE-OS) No. 26 52 656. Other constructions of this general kind are also disclosed in German laid open applications (DE-OS) Nos. 25 51 779 and 20 23 598.